Mandrel for winding cores



June 11, 1968 f/vx/EA/ 7-02 JOHN is. WILSON 3,337,799 MANDREL FUR WHNBING John L. Wilson, Cohasset, Mass, assignor to Union Associates, inc, Fitehhurg, Mass a corporation of Massachusetts Filed den. 3, 1967, Ser. No. 6%,644 11 Qlaims. (Si. Mil-72} ABSTRACT 6F THE DiSCLflSU-RE A mandrel for cores used in winding sheet materials has circumferentially-spaced slots receiving sprags. Shoulclers on the sprags are received in concave roots in the slots, acting as fulcrums for tilting of the sprags in either angular direction from a rest position. A core is centered by equal tilting of all the sprags, when the mandrel is rotated in either direction.

Backgrozmd and brief description of the invention It is conventional practice to wind and unwind sheet and web materials on hollow cylindrical cores of cardboard or fiber; for example, finished paper is removed from paper-making machines onto a core mounted on a power-driven mandrel or winder shaft. The core must be centered accurately on the axis of rotation of the supporting mandrel in order to maintain uniform tension and braking or driving torque, particularly when the roll of material has a substantial weight. Furthermore, the mandrel should be adaptable to accommodate cores of different diameters; and must exert sufficient gripping force to hold the core securely in spite of the increasing torque occasioned by an increasing roll diameter. At the same time, it should be capable of easy and rapid assembly with, and subsequent removal from, the core. Maintenance should be simple enough to be performed in the field.

It has previously been proposed to provide a mandrel which is of smaller diameter than the hollow core, having sprags or dogs circumferentially spaced about its surface, which are free to pivot outwardly to grip the inner surface of the core and support it in self-centering relation to the axis of the mandrel. This type of mandrel presents many advantages. However, previously-known mandrcls of this type are unidirectional in operation, and cannot grip a core for winding or unwinding in opposite rotational senses. Consequetly, it is necessary to reverse the mandrel relative to the core if the winding is to be followed by unwinding, or vice versa; and care must be taken that the mandrel is positioned in proper end-for-end relation, depending on whether it is to wind or unwind.

It is a primary object of the present invention to provide an improved winding mandrel which has a highly positive self-centering gripping action, and is operable in either direction of angular rotation. It is a further object to provide a winding mandrel having improved sprags or locking blades.

I provide a mandrel including a shaft having a plurality of circumferentially-spaced slots extending longitudinally or with longitudinal components of direction. The root portion of each slot joints its side walls in a pair of root concavities, preferably of V-section. A sprag or locking lade is received in each slot, and has a pair of shoulders at its base, spaced apart a distance equal or similar to that between the concavities of the slot and preferably of a convex V-section. Either shoulder may cooperate with a corresponding one of the concavities to act as a fulcrum for tilting the sprag in either angular direction from a rest position, about an axis longitudinal to the shaft. The slots are so formed as to provide clearance for the tilting 3,3317% Patented June Ill, 1968 movement. Each sprag has an apical gripping surface vhich extends circumferentially of the shaft in the rest position; depending on the sense of tilting, one or the other terminus of this gripping surface engages the core. The application of torque to the shaft as winding begins causes all or" the sprags to tilt equally in a common angular direction, centering the core on the shaft axis. Return of the sprags to their rest positions, to release the core as the winding or unwinding operation is completed, can be obtained simply by relief of the torque, or by springs. In some cases, it may be desirable to provide pneumatic or hydraulic means for tilting the sprags to engage the core, for returr them to the rest position, or both.

While the invention concludes with claims particularly pointing out the subject matter which I regard as my invention, it is believed that a clearer understanding maybe gained from the following description of a preferred embo ment thereof, referring to the accompanying drawing, in which:

FIGURE 1 is a view in elevation and partially in crosssection of a preferred embodiment of the improved mandrel;

is a sectional view taken along line 22 in FIGURE 1, looking in the direction of the arrows; and

FIGURE 3 is a fragmentary sectional view taken similarly to FIGURE 2, but showing a winding core in place and gripped by the mandrel.

Referring to the drawing, the mandrel includes a shaft to whose ends are stepped, as shown at 13, to receive end caps 1 and extend into axle portions 12 for supporting the mandrel in bearing blocks. Suitable arrangements may be made according to customary practice for driving or braking the shaft, spending on its use as a winding or unwinding shaft.

The shaft is formed with a plurality of circumferentially-spaced slots extending longitudinally, and three equiangularlys aced slots are provided in the preferred embodiment. -t should be noted that these slots may have a circumferential as well as a longitudinal component of direction, although ease of manufacture favors longitudinal slots as shown in the drawing. Received in each slot is a sprag or locking blade 20, which has a curved gripping surface 22 formed with a series of longitudinal teeth for securely engaging the internal surface of a hollow cylindrical Wil ing core 23. The core is usually made of paper, cardboard or the like, and the illustrated sawlilce teeth can imbed themselves securely in the surface.

At rest, the sprags occupy the positions shown in FIG- URE 2, in which their illustrated radial axes of symmetry are aligned with radii of the shaft. In this position, a pair of spaced-apart shoulders 31 (see FIGURE 3) rest in root concavities 19 terminating the root portion 29 of the corresponding slot, and the gripping surface 22 extends circumferentially of the shaft. In the preferred configuration, the side walls of each slot 18 are parallel, while the side surfaces 27 of each sprag converge from its shoulders 13; toward the termini 23 of its gripping surface. The sprag is thus free to tilt in either circumferential direction, rocking about one of its shoulders, on a correspondin; concavity 19 as a fulcrum. The side walls of slots 18 may alternatively, for example diverge radially outwardly, with the surfaces 27 being parallel. It is necessary that clearance be provided for tilting in either angular sense. The shoulders 31 and concavities 19 shown have a V- section, but some radius of curvature of either part, which will permit freedom for tilting motion, is satisfactory. The base surface 28 of the sprag and the root portion 29 of the slot exhibit a congruent V-section, which serves to increase the cross-sectional moment of inertia of the sprag and thus its stiiiness.

The sprags are resiliently biased toward the rest posi- 3 tion by means of springs 24, interposed between axiallyextending flange portions formed in the end caps 14, and lips 26 of reduced height extending from the ends of the sprags. The mandrel is held in assembled relation by means of screws 16 passing radially through the end caps 14 and threaded into the shaft.

The diameter of a circle tangent to the gripping surfaces 22 of the sprags in the rest position is slightly smaller than the inside diameter of the winding core 21, so that the latter may be freely assembled with the mandrel when at rest. In the illustration of FIG. 3, a core 21 is shown engaged on the mandrel and winding a length of sheet material The parts are driven in the direction shown by the arrows by suitable motive means connected with the shaft 15, against back tension applied to the sheet. As the shaft it) initially commences to rotate, with the sprags in the rest posiion of FIG. 2 and the core resting upon upwardly-disposed ones of the sprags 2-3, the applied torque causes this sprag or sprags to rock about one of the shoulders 31, with the corresponding root concavity 19 acting as a fulcrum. The sprag tilts circumferentially of the shaft as shown, causing a portion of its gripping surface 22 to rise and engage the inner surface of the core. As the core is raised, it engages the gripping surfaces of any sprags which are disposed downwardly, and these tilt in the same angular direction to engage and center the core on the axis of rotation of the mandrel. It will be apparent that rotation in an opposite angular direction will result in a similar self-centering gripping action, with the sprags tilting about their opposite shoulders. At the completion of the winding or unwinding operation, as the torque is relieved and the core and mandrel are brought to rest, gravitation causes the sprags to tilt to their rest positions, lowering the core and releasing it for re moval from the mandrel. This releasing action is aided by the bias of the springs 24.

In some applications, it may prove necessary or desirable to provide pneumatic or hydraulic means for tilting the sprags from their rest positions into engagement with the core, and my invention contemplates the provision of suitable means adapted to this purpose. It will be readily apparent to those skilled in the art that various additional changes and modifications may be made in the improved mandrel without departing from the true spirit and scope of the invention, which I intend to define in the appended claims without limitation to the details of the illustrated embodiment.

What I claim is:

1. A mandrel for supporting a core for winding and unwinding material of indefinite length, comprising:

a rotatable shaft having a peripheral surface formed with a plurality of circumferentially-spaced longitudinally-extending slots;

and a plurality of sprags received in longitudinally-extending relation in said slots for tilting movement therein;

each of said sprags having a cross-sectional form including an apical gripping surface protruding from the receiving slot for engaging an inner surface of a hollow cylindrical core, and a basal pair of spacedapart shoulder areas located on opposite sides of a cross-sectional axis of symmetry;

each of said slots having opposed side walls joining a root portion in a pair of spaced-apart root concavity areas, and being formed so that a sprag may assume a rest position therein with its said axis of symmetry substantially radial to said shaft, and with its said shoulder areas resting in said root concavity areas: each of said sprags being tiltable in either angular direction about a corresponding one of its said shoulder areas, resting in a corresponding root concavity area as a fulcrum, to elevate said gripping surface from said peripheral surface into rotational driving engagernent with the supported core.

2. A mandrel as recited in claim 1, in which said gripping surface of each said sprag is curved to extend substantially circumferentially of said peripheral surface when the sprag is at rest, said gripping surface extending between termin ls spaced apart on opposite sides of said axis of symmetry to present a substantial width of gripping surface between either of said termini and said axis of symmetry.

3. A mandrel as recited in claim 1, in which said gripping surface is formed with a series of teeth having longitudinal extent along said sprag for gripping the core.

4. A mandrel as recited in claim 1, in which said gripping surface and said shoulders of each said sprag are joined by side surfaces converging from said shoulders toward said gripping surface.

5. A mandrel as recited in claim I, in which the spacing between said shoulders of each sprag is substantially equal to the spacing between said root cavities of the receiving slot, and said gripping surface is joined to said shoulders of each sprag by side surfaces converging, in a direction from said shoulders toward said gripping surface, away from said side walls of the receiving slot, such that the sprag is free to tilt in the slot in either circumferential direction.

6. A mandrel as recited in claim 1, together with spring means resiliently biasing each of said spragstoward said rest position to restore the sprags to the rest position upon the discontinuance of relative torque application between said shaft and a core gripped by said sprags.

7. A mandrel as recited in claim 1, in which there are three said slots spaced circumferentially about said shaft and three said sprags received in said slots.

3. A mandrel as recited in claim '1, in which each of said sprags terminates in an axially-extending lip of re-.

ferentially about the retaining lips of said sprags, together with compression spring means interposed between said flange portion and said lips to bias said sprags toward their rest positions.

9. A mandrel as recited in claim 1, in which said root portion of each of said slots has a concave V-section, and each of said sprags is formed with a convex base surface of V-section receivable conformably in said root portion of a corresponding slot.

r10. A mandrel as recited in claim 1, in which said shoulders of said sprags are of V-section.

l1. -A mandrel as recited in claim 1, in which said root concavities are of V-section.

References Cited UNITED STATES PATENTS 2,171,300 9/1939 Mann 24272 3,001,736 9/1961 Schultz et al 242-72 FRANK J. COHEN, Primary Examiner.

N. L. MINTZ, Assistant Examiner. 

